1. Field of the Invention
This invention relates to crystalline polyolefin resin compositions comprising specific crystalline polyolefins and specific organic phosphorus compounds, said polyolefin resin being produced in the presence of a Ziegler type complex catalyst, namely a Ziegler catalyst, a Ziegler-Natta catalyst or any modification thereof, supported on a halogen-containing magnesium compound such as magnesium chloride and not subjected to a catalyst residue-removal step. More particularly, this invention relates to novel crystalline polyolefin resin compositions in which the weathering properties of such polyolefin resins with catalyst residue unremoved have been improved.
2. Description of the Prior Art
When a Ziegler type complex catalyst supported on a halogen-containing magnesium compound is used, the yield of polymer per a given amount of a transition metal which is the main component of the catalyst (such as titanium) is several hundreds to tens of hundreds times as much as the yield obtained when an unsupported catalyst is used such as the catalyst system comprising diethylaluminium monochloride and an activated titanium trichloride-aluminium chloride mixture which has been prepared by reducing titanium tetrachloride with metallic aluminium and milling the reaction product. Moreover, a high-crystalline polymer can be obtained by using the supported catalyst. Thus, the above-mentioned catalysts have been noted as novel catalysts which do not need removal of the catalyst residues or extraction of the amorphous polymer from the resulting polyolefin resins. Typical examples of such novel catalysts are disclosed in Japanese Laid-Open Patent Publication Nos. 9342/1972 and 126590/1975 Specifications.
Such supported catalysts provide higher polymer yield per amount of a transition metal which is the main component of the catalyst, but the concentration of the transition metal supported on the given amount of carriers is low. Thus, there arise the adverse effects of the remaining carriers on the polyolefin resins with the catalyst residue unremoved. In other words, the amount of a transition metal component supported on the carrier is from less than 1% to 10% at the most by weight of the solid catalyst component. The yield of polymer per the carrier (magnesium compound) is from several thousands to tens of thousands at the most. Thus, the thermal stability, odor, color, anticorrosivity, weathering property and other properties of the molded polymer products may be impaired by the magnesium compounds (usually magnesium halides) contained in the polymers which have not been subjected to a catalyst residue-removal step. It has been especially important to solve the problem of low weatherability, since large quantities of molded polyolefin resin products are used outdoors.